1. Field of the Invention
The present invention relates to a locking mechanism for a utility knife, and more particularly to a quick release locking mechanism for a utility knife, wherein the locking mechanism may be used with a utility knife having a metal housing or may be integral with the blade carrier and/or return spring in an automatically retractable utility knife.
2. Description of the Related Art
Utility knives are well known in the art, and typically include a housing, which is often constructed of separable halves, a blade carrier, which holds a razor or other blade, and a handle or thumb piece attached to the blade carrier and extending from the housing to enable the blade to be extended from and retracted into the housing. Utility knives are available in automatically retractable and indexed versions.
In an automatically retractable utility knife, a spring is attached between the housing and the blade carrier to automatically retract the blade into the housing upon release of the thumb piece. The spring tension is such that when the blade is projected and inserted in a material being cut, e.g., cardboard, the friction between the blade and the material is sufficient to retain the blade in the projected position. In an indexed utility knife, the blade may be moved between one of several locked positions, including fully retracted and fully extended positions.
In many utility knives, the housing is constructed of two halves which are attached by means of a screw located toward the center of the housing. In order to replace the blade, it is necessary to unscrew the halves of the housing, which requires a screwdriver, and which is both time consuming and inconvenient. To overcome this shortcoming, utility knives with plastic housings have been developed that incorporate a locking mechanism that may be released without tools. For example, U.S. Pat. No. 5,121,544 relates to a utility knife that is constructed of separable plastic halves and that includes a rear snap-locking mechanism. In order to operate the locking mechanism, the user must push an actuating lever and slide the halves in opposite directions generally parallel to a central axis of the housing, i.e., generally parallel to the direction of movement of the blade, before the halves release from each other.
Commonly-owned U.S. Pat. Nos. 6,058,607 and 5,813,121, the contents of which are incorporated herein by reference, disclose a utility knife locking mechanism that includes a resilient locking arm on a first half of the housing, and a locking aperture on the other half of the housing. In use, the locking arm is pushed into the locking aperture to lock the halves of the housing together. When the locking arm is depressed, it becomes released from the locking aperture to allow the housing to be opened.
Quick-release locking mechanisms of this type have been utilized only in plastic knives, in which the locking mechanism may be molded integrally with the housing, and in which the materials are sufficiently flexible to enable the locking arm to be released. Such locking mechanisms have not been used in metal housings, since the metals used are often too rigid to be used in the locking mechanism.
Accordingly, it would be desirable to have a quick-release locking mechanism for a utility knife that may be used with knife having a metallic housing. More generally, it would be desirable to have a quick-release locking mechanism for a utility knife that is separable from the housing itself so that the locking mechanism may be used with housings constructed of materials unsuitable for being constructed integral with the locking mechanism.
The present invention is a cutting device comprising (i) a housing having first and second separable portions, the first portion comprising a locking aperture, the second portion comprising an attachment aperture, and (ii) a locking apparatus for removably locking the first and second portions of the housing. The locking apparatus comprises an attachment portion for being fixedly attached in the attachment aperture, and a locking arm adapted to be removably locked into the locking aperture. The attachment aperture and locking aperture are correspondingly positioned so that the locking arm becomes aligned with the locking aperture when the first and second portions of the housing are aligned for assembly. If desired, the housing may be constructed of metal, and the locking apparatus constructed of resilient plastic, such as Celcon, ABS, or Polycarbobate. The locking apparatus may also comprise a return spring and blade carrier integrally molded therewith.
In one embodiment, the locking arm comprises i) an upstanding portion oriented generally perpendicular to an axis of the housing, ii) an actuating arm extending laterally from a free end of the upstanding portion, so that downward force on the actuating arm causes a bending of the upstanding portion, and iii) a locking lip toward the free end of the upstanding portion extending laterally in a direction opposite to the direction of bending of the upstanding portion. The attachment aperture comprises at least one attachment shoulder, and the attachment portion of the locking apparatus comprises at least one corresponding extension for being locked in the attachment aperture against the attachment shoulder.
In an improved cutting device having a housing formed of first and second portions, a return spring, and a blade carrier biased by the return spring, the improvement comprises a locking apparatus for releasably attaching the first and second portions of the housing, the locking apparatus being integrally molded with the return spring and the blade carrier. In one embodiment, (i) the first portion of the housing comprises a locking aperture, and the second portion of the housing comprises an attachment aperture, and (ii) the locking apparatus comprises an attachment portion for being fixedly attached in the attachment aperture, and a locking arm adapted to be removably locked into the locking aperture. The attachment aperture and locking aperture are correspondingly positioned so that the locking arm becomes aligned with the locking aperture when the first and second portions of the housing are aligned for assembly. If desired, the housing may be constructed of metal, and the locking apparatus constructed of plastic.
Also disclosed is a cutting device comprising a housing and an integrally molded A blade carrier, return spring, and releasable housing lock disposed within the housing.
Another embodiment of the invention discloses a cutting device comprising (i) a metallic housing comprising first and second separable portions, and (ii) a plastic locking apparatus for removably locking the first and second portions of the housing, the locking apparatus comprising an attachment portion for being fixedly attached to the first portion of the housing, and a locking arm adapted to be removably locked to the second portion of the housing.